1. Field of the Invention
This invention relates to a composite article comprising a support member, a controlled release material coated onto the support member, and an inorganic pigment; and a method of making the same. The composite article is useful in thermal imaging.
2. Description of the Related Art
Vapor deposited metallic thermal transfer ribbons typically require a release layer interposed between the metallic material to be transferred and the ribbon support in order for the metal to be effectively thermally transferred from the ribbon. Commercial thermal mass transfer printers are typically capable of providing a thermal transfer energy to the ribbons in the range from about 1-3 J/cm.sup.2. To produce high resolution images, a vapor deposited metallic thermal transfer ribbon should be constructed such that during thermal imaging at low thermal transfer energies (preferably, less than about 3 J/cm.sup.2), the vapor deposited metal transfers from the ribbon at the printed areas and adheres to the ribbon at the non-printed areas.
Various attempts have been made to lower the adhesion of vapor deposited metal to the support member. Such attempts have generally been limited to use of chemical release coatings. Suitable chemical release coatings have a lower surface energy with respect to the support member than with respect to the vapor deposited metal, or vice versa, depending on the particular transfer application.
For example, in the September, 1988, issue of Office Equipment and Products, an article entitled "Matsushita Takes a Giant Step Forward With Its Ribbon Technology," described a metal thermal transfer ribbon having a 0.01 micrometer thick exfoliation layer.
A paper entitled "New Color Thermal Transfer Printing Media" presented to "The 5th International Congress on Advances in Non-Impact Printing Technologies" in San Diego, Calif., Nov. 12-17, 1989, described a thermal metallic transfer ribbon having an anchoring layer interposed between the vapor deposited metal and a release layer to secure the vapor deposited metal to the release layer.
U.S. Pat. No. 4,868,049, (Nelson) teaches a transfer sheet comprising, in successive layers, a carrier film, a metallic film, and an adhesive. Optionally, the transfer sheet further comprises, in successive layers, a release coat and a polymer coat interposed between the carrier film and the metallic film, and a primer coat interposed between the metallic film and adhesive. A preferred release coat is said to be made from an ethylene vinyl acetate copolymer.
U.S. Pat. No. 4,892,602, (Oike et al.) discloses a heat-sensitive medium comprising a support, and a transfer layer comprising a protective resin layer, a metal deposition layer, and an adhesive layer, said three layers being provided in that order from the supporting side. Optionally, a lubricant layer may be interposed between the protective resin layer and the support.
U.S. Pat. No. 4,875,961, (Oike et al) discloses a heat-sensitive medium comprising a support, and a transfer layer comprising at least a non-flowable ink layer and an adhesive layer, said two layers being provided in that order from the support side. Optionally, a lubricant layer may be interposed between the ink layer and the support.
While chemical release coatings have had some success in providing for good transfer of vapor deposited metal from a vapor deposited metallic transfer ribbon, there is still a need to improve such means for transferring the vapor deposited metal and to improve the resolution of images produced from such transfer ribbons.